Gypsum improves and maintains the health and hardwearing properties of all amenity turfs. It helps in two ways.
It improves soil structure and it supplies calcium and sulphur, both essential plant nutrients.
The most significant problem for managers of most amenity turfs is the compaction of the underlying soil that arises
from heavy foot traffic. A compacted soil leads to slow growth and slow growth means slow recovery from traffic
damage - a vicious circle. There are a number of reasons why soil compaction slows plant growth. Root penetration is
impeded (mechanically), drainage is reduced (in wet weather the surface is prone to flooding and the soil becomes
anaerobic) and, in the summer, rain and irrigation water tends to runs off (rather than to penetrate through to the
roots leading to earlier onset drought). In addition, during winter, a turf prone to waterlogging is less resistant to
scuffing as it regains firmness more slowly after rainfall so that foot-traffic and mower damage is exacerbated.
Gypsum is well known to improve soil structure and drainage and to alleviate compaction so its regular use with turf
reduces many of these problems. Gypsum is best applied following physical soil-aeration treatments (coring, verti-draining,
vibra-moling etc) but can be sprinkled on at any time. As the pH of gypsum is neutral, excessive applications are not
damaging so rates can be quite high - especially in areas having particularly acute soil problems.
Regular gypsum applications can minimise the ingress of shallow rooting Poa grasses and weed species. For new or existing
turf areas, sprinkle ½-1 kg per square metre but for a heavy-clay soil up to 2 kg per square metre may be applied.
Conveniently, 1 kg of gypsum has a volume of about 1 litre so it may be easier to use a volume measure, especially where
spot treatment is being carried out.
Rapid growth for high health and quick repair means that the nutritional needs of the turf should be supplied.
Gypsum is a good source of the plant nutrients, sulphur and calcium.
Sulphur is important for the production of green, protein-rich,
leaves while calcium is important for plant health. The levels of both are high in leaves so are regularly removed from
the sward by mowing. Used as a fertiliser, application rates will be lower than when used to remedy a severe soil
condition (closer to 1 kg/2m
2 each year). If, instead, gypsum is broadcast onto the turf surface at regular intervals
during the year at about 1 kg/5m
2, advantage is taken of the electrolyte effect of gypsum. This minimises the dispersion
of clay particles but lasts only while the gypsum is present on the surface.
Gypsum increases soil microbial activity and encourages worms, speeding up the decomposition of organic matter. Where
clippings are mulched and left on the turf rather than being removed, regular applications of gypsum will help speed up
their breakdown and the eventual return of organic matter and nutrients to the soil.
It is difficult to exclude small children and wildlife from public areas so management should employ 'friendly' methods
wherever possible. Gypsum is a natural, non-toxic mineral that is certified for use in organic production. Even when
applied at very high levels it will not damage animals, soil or plants. Also, gypsum's neutral pH means that where it is
used in parks for high-traffic areas of turf lying close to rhododendrons and camellias it will not raise soil pH and so
damage these acid-loving plants (lime would).
Application of gypsum to turf improves:
- Playability of winter sports fields
- Trafficability of lawns (especially after rain)
- Durability of racetracks
- Seedbed conditions for new turf
- Efficiency of irrigation
- Oxygen supply to roots
- Plant health, growth and repair rates.
